Psychic side of a tornado

Rear flank downdraft

Definition:Rear flank downdraft is the name for a cool dry air that is wrapping around a mesocycloon. This means, the rear flank downdraft is an announcer of a tornado. When you watch Storm chasers on Discovery, you hear that they use this term a lot. This term is a perfect announcer to announce that the conditions are perfect to form a tornado on that spot.

Rear flank downdraft:There is a perfect explanation about the way a rear flank downdraft works. I will show that with a picture that shows it a lot better. This is a picture of a super cell viewed from above the sky. As you can see there are isotherms in the picture (this is the line with the globules and the triangles). This is a sort of line that connects the same pressure (most of the time with a difference of 5 mill bars) with a line. The triangles and globules show whether the air is warm or cold. You can see that cold air is moving to the center in the mesocyclone. There it changes into an Occluded front. This air is perfect to form a tornado.

Occluded front:When the Occluded front is made, the mesocyclone begins to show some convection. This convection is really important to form a tornado. Without convection, there can’t be a tornado. So the Occluded front is one of the most important things for a mesocyclone to develop. But the Occluded front can only be formed if there is a rear flank downdraft.

Radar:A rear flank downdraft can be seen perfectly on radar. This is a first sign of a tornado production. The picture on the left is showing a rear flank downdraft on the radar. You can see this by the sort of angle in a supercell. This is shown perfectly in this picture. This is a rear flank downdraft that intercepts the first beginnings of an Occluded front.

Sources:

http://www.nssl.noaa.gov/primer/tornado/images/tor_supercell_above.jpghttp://www.weeramateur.nl/uitleg.htmhttp://en.wikipedia.org/wiki/Occluded_fronthttp://www.ncdc.noaa.gov/nexradinv/